Trypsin is one of the most widely studied serine proteases because it is responsible for the normal physiological functioning of cells such as digestion, coagulation of blood, immune responses and blood pressure regulation.
Phenolic compounds are ubiquitous and abundant vegetable secondary metabolites in the human diet and are capable of inhibiting major digestive enzymes.
Polyphenols were extracted from the leaves of three Nigerian vegetables, Amaranthus viridis (AV), Solanum macrocarpon (SM) and Telfairia occidentalis (TO) using 1:20 ground leaf powder to water ratio at 60°C. The vegetables were cultivated using different doses (0, 20, 40, 60 and 80 kg ha-1) of urea fertilizer applied either at the time of planting or two weeks after planting.
Effects of fertilizer micro dosing, time of application and vegetable variety on the inhibition of trypsin by polyphenol extracts from these vegetable leaves and mode of inhibition of trypsin activities via kinetic studies in the absence and presence of the vegetable extracts was also investigated.
In general, trypsin inhibition increased with increases in concentration of the polyphenolic-rich extract.
It was also observed that AV (44.25%) significantly (p<0.05) exhibited higher inhibitory activities than TO (6.30%) and SM (19.21%). Lineweaver-Burk plot results indicate that the polyphenolic compounds interacted with the enzyme active site to reduce substrate binding as evident in the competitive mode of action.
We conclude that AV polyphenols have stronger binding affinity for trypsin and are better inhibitors of this enzyme when compared to TO and SM.